Metallurgical process



y 30, 1961 M. c. UDY 2,986,459

METALLURGICAL PROCESS Filed Dec. 4, 1959 Chromite Ore or Concentrate orBlended Iron Oxide-Chromite h ro m }je Qrg Reduction Burden Hon (ireEssential Carbonaceous i Fluxes Reductant i I Calcining and I Calciningand {I Calcining and I: Pre-Reduction Pre-Reduction Pre-Reduction l UmtUmt Umt l l Stabilized, Free- Stabilized, Free- Stabilized, Free-Flowing Sinter Flowing Sinter Flowing Sinter Carbonaceous CarbonaceousReductant Smelting Smelting Reductant Furnace Furnace Waste High- CarbonLow- Carbon Chromium Waste Slag Iron-Chrome Metallic Oxide Slag Alloylron Slag Holding or Blending Furnace Chromium-Iron Master Steel AlloyLow C and Si Oxygen or Non-Carbonaceous oxide Reductant Steel Refining(return of oxidized Furnace chromium or manganese v Alloying to metallicphase) l l Adjustments Finished Slag to 'NVENTQR Steel to M|ll WasteMurray C. Udy

United States Patent 2,986,459: METALLURGICAL PROCESS Murray C. Udy,Niagara Falls, N.Y., assignor to Strategic-Udy Metallurgical andChemical Processes, Ltd., Hamilton, Ontario, Canada- Filed Dec. 4, 1959,Ser. No. 857,293 9 Claims. CI. 75-40 This invention relates in generalto'metallurgy and has ior its principal object the provision of a' newand improved process for producing chrome-iron alloys of con trolledsilicon-carbon contents and special grades of finished steels directlyfrom chromite ores and concentrates, including conventional high-gradeores,-m-arginal and low: grade chromite ores of chromium-toiron ratiosas low as 0.5 to 1.0, and various physical mixtures or blends of ironoxideand chromium oxide-bearing materials as shown by the accompanyingflow sheet. Specifically, the invention involves the provision of aunique carbothermic reduction of either raw or previously concentratedmaterials of the general class'defined for the production and recoveryof valuable low-carbon chrome-iron master alloys which can be processedto provide a wide variety of finished steels including, by way ofillustration, straight ferritic or maltensitic chromium steels of theSeries 400 and .5 types, austenitic nickel-chromium stainless steels ofthe so-called Strauss or Series 300 types, such as the popular 18-8stainless steel, modified chromium-nickel .steels such as thesilicon-containing Rezistal type of :austenitic alloys, low-chromium andchromium-vanadium toolsteels, manganese-chromium steels, and the like.-The accompanying flow sheet shows various modifica- .tions of theinvention.-

Heretofore, it has been considered axiomatic that the processing ofchromite ores and particularly low chromium-to-iron ratio oxidicreduction burdens should proceed via various preliminary beneficiationoperations aimed at attaining intermediate products of chromium-to-ironratios within ther-ange of from 3 to 5 parts chromium to each part iron,namely, products which are amenable .to

2,986,456 Patented May 30, 1961 2 chromium alloy of oil-grade orrelatively low-chromium content,and a molten slag product of relativelyenriched chromium oxide content containing iron in any desiredproportion lower than that of the original raw charge material. Inessence, in accordance with the process of said copending application,the initial smelting operation is conducted to adjust the chromezironratio within the slag to any j desired value according to the exactnature of the ferrochrome alloy sought to be recovered within asubsequent smelting operation or openations conducted with thechromium-enriched, i.e., iron degrade'd, slag recovered from the firststage, while at the same time placing the residual chromium oxide valuespresent in the slag in con-- dition for substantially complete reductionand settlingout or recovery 'of' the metallic chromium from the ultimatewasteslag product produced in said subsequent treatment by existingmethods for the production of high have been directed to methods forrendering thelow-gradechromites amenable for treatment via techniquesdeveloped and adopted by industry in conjunction with the processing ofhigh-grade chromite ores to steelmaking ferroalloys. For example, .incopending United States application Serial Number 731,993, which wasfiled by.

Marvin I. Udy on April 30, 1958, now Patent No. 2,934,- 422, grantedApril 26, 1960, there are described and claimed a series of relatedprocesses which are directed to the multi-stage smelting ofchromite-bearing materials for the production and recovery'of so-calledstandard grades of ferrochromium. In accordance with the proc-.

esses of said copending application, a natural chromite ore orconcentrate of relatively low Cr-zFe ratio is beneficiated for ultimateuse in the production of ferrochromium alloys by an initial carbothermicsmelting operation, conducted for the selective reduction and removal ofex-.

cess iron present in the ore or concentrate, with the production andrecovery of low-carbon metallic iron of controlled low-chromium contentor a high-carbon ferrosmelting operation or operations. In processingthe residual chrome-enriched slag from the first stage forthe productionof high-carbon and medium-carbon ferrocliromium products, a secondsmelting operation is required whereas, if the enriched slag is to beprocessed to low carbon ferrochromium, two or even three additionalstages any attempted .direct or even selective carbothermic re-.

duction type of operation.

It has been postulated that non-carbonaceous reductants such asferrosilicon or ferrochrornium siliconcan be employed to maintain carbonspecifications within tolearble boundaries, but experience demonstratesthat when low-silicon contents are also desired, aswould be the case inmost any steehn-aking operation since the silicon content of the meltmust be oxidized into the slag before decarburiza-tion can be effected,this type of reductant must be employed in deficient amounts, i.e., inquantities less than the stoichiometric requirements of the containediron oxide and chromium oxide contents of the starting ma-.

terial, with the result that a consequent sacrifice in the yield ofmetal obtained becomes necessary. Needless to say, such a sacrificebecomes impossible, economically, when one is concerned with themarginal or low-grade chrome-iron starting materials.

In order to understand the full significance of the process of myinvention, it is essential to understand current industrial practiceswith respect to. the production of,

stainless steels. Thus, with very few exceptions the production offerroalloys employed in steelmak-ing is effected.

independently of the steelmaking operation, per -se, but in any event,the ferroalloy producer devotes considerfor use in the production ofSeries 300 steels. plained hereinbefore, much of the expense incidentalto the production of these steelmaking alloys exists with respect to thesimple procurement of raw materials which are suitably deficient in ironor at least favorably constituted for the elimination of excess iron,but this fac tor is actuallyof no basic importance since the steel makermust ultimately introduce iron into his melt to produce any of thecommercially important stainless steels. That is to say, while theferroalloy producer goes to considerable added effort and expense toprovide relatively low-iron alloys of base constitution corresponding tothe alloying metals chromium and nickel, for example,

the steelmakers ultimate use of these alloys is predicated upon irondilution practices which almost invariably reestablish theirend-products as iron base alloys.

Considering the faetthat the cost of the contained chromium inlow-carbon .ferrochromium, for example, currently ranges from about3.71m 41 cents per pound, and the cost of contained nickel in equivalentferroniclirel alloys currently ranges from about 60 cents to over onedollar per pound, it becomes abundantly clear why the production ofstainless steels by existing methods represents such a costlyundertaking. In addition to these initial production costs, it iscustomary for the steelmaker to'oxidize substantial carbon out of thesteel melt by means of ore or oxygen which results in oxidation ofappreciable chromium into the slag phase. To recover these valuesfollowing decarburization and refining of the melt, the steelmaker mustthen use various expensive deoxidizing or reducing agents such assilicon metal, ferrosilicon, aluminum, etc. The combined efiectof theuse of high-grade starting materials, strict adherence to socalledstandard alloys, and the extensive refining and post-refining reductionoperations practiced by. the steelmaker hasbrought the most commonstainless steels to current price levels within the range of from 350 to600 dollars per' net ton, even in semi-finished slab or billet forms.

It its broadest aspect, the process of my invention is directed to theprovision of a unique tandem stage reduction technique for the treatmentof chromite ores or admixed chromite and iron oxide-bearing materials ofvirtually any chrome-iron ratio to derive a low-carbon stainless steelmaster alloy of predetermined iron and chrocontents correspondingsubstantially to the precise proportion of these metals desired inaparticular grade of finished steel. In other aspects, and particularlythose pertaining to the utilization of extremely low chrome-toir'onratio starting materials, the invention departs from existingconventions which dictate that these materials must- -be processedinitially to standard grades of ferrochromium, and provides via a tandemreduction smelting arrangement "a chromium-iron alloy which may beprocessed directly within aiconventio'nal steelmaking furnace to producevirtually any type offinished steel. Common to all aspects 'of myinvention is the utilization of a unique tandem reduction technique inwhichl a portion of a combined oxidic'reduction burden of chromium andiron is subjected to c arbothermic reduction to derive an ironchromiumalloy of relatively high-carbon content, whereias the remainder of saidreduction burden is simultaneously subjected to carhothe-rmic reductionto derive metallic iron of low-carbon content and a chrome-rich slag forrecycle to the iron-chromium alloy-production stage of the tandemreduction cycle. The metallic products of the two furnaces are'thenrecombined in molten form to provide arelatively low-carbon master alloyof iron and chromium which may be processed directly by stand:

ard procedure sor refining to produce stainless steel "of:

any desired composition;

Essentially, the process of the invention is based, ,at

least in part, on the observation that whereas carbon controlisdiflicult to achieve under. conditions involving the simultaneousdirectreduction of bothchromium oxide and iron oxide and generallynecessitates sacrificing a portion of the total available" chromiumtothe slag phase, carbon control to extremely low values can be read} ilymaintained in the selective, reduction of iron only from such a mixedoxidic reduction burden. In accordance with a preferred process of theinvention, the aforementioned phenomena are utilizedtoipermit.maximumfchromium re duction with iron from one fraction of amixed chromium oxide-iron oxide reduction burden of natural or.synthetic t n dlf igin; w thout r ga d. o c on mam,

subjected to selective carbothermic reduction to produce low-carbonmetallic iron or semi-steel. The metallic products of the tandem directand selective reduction operations are then recombined in properproportions to yield a controlled carbon content master alloy ofchromium and iron ratio approximately equivalent to the preciseproportions desired in the final steel product, namely, alloys rangingfrom .60-90 percent iron and 10- 40 percent chromium. The reconstitutedmaster alloy requires only mild refining and alloying additions, asdesired, to yield virtually any grade of'finished steel. To provide abalanced, closed system with respect to total incoming chromium values,the chromiumrich slag produced in the iron production phaseof the tandemreduction operation is'recycled, preferably in molten form, to thedirect reduction stage for addition to its fraction in the production offurther quantities of the high-carbon iron-chromium alloy.

It is believed that the foregoing process measures may behest understoodby reference to the following detailed description of specificembodiments of the invention taken in conjunction with the accompanyingdrawing, wherein the single figure constitutes a schematic flow diagramor flow sheet illustrating the exact sequence of steps or operationsinvolved in the processing of a typical iron oxidechromiurn oxidereduction burden to a finished stainless or corrosion-resistant steel.

In the practice of the process of my invention, a

- chromite ore or concentrate, or such a material blended necessaryfluxing additions, and the combined mass is tion of the resultingiron-chromium product produced,

this the smea s. its sites was use i then calcined to produce asubstantially stabilized reduction burden of predetermined base-acidratio. In either event, I prefer to follow the unique fluxing techfliqles described in the above-mentioned US. Patent to Marvin I. Ucly,although the base-acid ratios of the slag systems of the presentinvention may be constituted at optimum values anywhere within the rangeof from one to twoand-one-quarter (LO-2.25) parts by weight base(calculated as MgO and excluding iron oxide) to each part by weight ofsilica, and entirely satisfactory results are obtained.

l The iiuxed charge is calcined by heating within any suitableapparatus, such as a rotary kiln, for example, to establish it at. themaximum possible temperature for a free-flowing consistency, withoutoverheating to the extent that the charge will form rings within thekiln. Ordinarily, this can be accomplished quite readily by heating thecharge to a temperature within the range of from 1100to 1300 C. Ofcourse, the split char ges can be melted directly within the tandemelectric furnaces, but

I find that the use of a kiln with gas, oil, coal or even waste gasesfrom an electric furnace, provides a more economical operation ascompared with theuseof. electrical energy exclusively. Furthermore, Iprefer to operate within the successive smelting and refining stages ofthe process of the invention with molten charge from a preceding stagein order to further economize on power consumption by avoiding thenecessity for remelting these materials I also find it to beadvantageous to practicesorne pre -reduction. within the kiln by thedirect addition of .a portion of the overallcarbonaceous reducan the k na e nsistsat lfr e, ith the p mary objective of maintaining through-putthe kiln for supplying the tandem electric furnaces or equivalentsmelting units on a conti ous basis. Breredu ti n f chmmium O i lihq fl,

but it is found that from 33-60% oxygen removal can be eifected in thekiln while maintaining good throughput and avoiding any significantreduction of the chromium oxides contained in a reduction burden. 1

The hot, free-flowing partially reduced material discharged from thekiln is subdivided into two approximately equal-weight fractions. Thissubdivision and, in turn, the respective loads on the tandem furnacescan be regulated in accordance with the chrome-iron ratio of theoriginal material, as modified to the extent that any blending ispracticed in the formation of the iron oxidechromium oxide chargematerial. The fraction to be treated by direct and substantially totalreduction for" the production ofthe iron-chrome alloy is charged to thesmelting zone of one of the tandem electric furnaces maintained at atemperature within the range -offrom 1450-1750 0., together withadditional quantitiesofa -carbonaceous reductantinan amount suflicientto effect reduction to the metallic state of all of the-chromium oxideand iron oxide contained therein. The resulting metal product will havea chromium-iron ratio corresponding to that of the original ore orblended ores, but upgraded with respect to chromium content to anydesired extent by reason of the additional chromium oxide valuesrecycled from the tandem furnace operating on the selective reductioncycle for low-carbon iron. In view of the fact that the former furnaceis operated for maximum chromium recovery in the metal phase, the carboncontent in the iron-chrome alloy recovered will normally range upwardsto 6 percent. Where justified for any specific starting material, alower carbon content can be achieved in the iron-chrome alloy by leavinga portion of the chromium oxide content in the residual waste slagproduced in this furnace. In general, however, by reasons of the ease ofcarbon control attained through practice of the dilution technique ofthe invention, I prefer to effect maximum chromium reduction inthisphase of the tandem operation.

The remaining fraction of the kiln sinter is supplied to the smeltingzone of the second tandem furnace, which is also maintained at atemperature within the range of from l450l750 C., together with acontrolled quantity of carbonaceous reductant sufiicient to effect theselective reduction to the metallic state of the major. portion of theiron contained therein. In this connection, it is to be noted that in areduction operation of the class. described the metallic phase productcan be maintained .substantially free of carbon contamination until thee uaLirQn in. the Pha t fi hsaa is?! equivalen tna proximatq 6 w e er tec n i reduction of the charge under action of a carbonaceous reducingagent results in slight gradual carbon contamination of the metal untila residual level of approximately 3 4 percent iron-is reached in theslagphase, but attempted carbonaceous reduction beyond this 3-4; percentiron residue results in. rapid carbon contamination of the metal. Withinthe range 3-8 percent iron unreduced in the slag, it is generally foundthat the major portion of the chromium is likewise retained in oxideform within the slag. At the upper limits of this range, namely, 6-8percent residual iron, it is possible to achieve carbon control withinthe range of from 0.2 to 0.5 percent, with a simultaneous low-chromiumcontent within the metallic iron phase product. Of course, provided thefull production of the tandem iron furnace is to be utilized fordilution of the carbon content in the highcarbon iron-chrome alloy fromthe other tandem furnace, it is relatively immaterial whether the ironproduct also contains a portion of the chromium in metallic form and,under these circumstances, the selective reduction is simply continuedto the maximum possible limit consist- .ent with the.carbon..level:desired in the metal phase.

On" the .otherhand, .it sometimes proves desirable to -.bleed a portionof the total iron productionout of the system for marketing or for usein theproduction of car-hon steel and, under'such circumstances, it isequally desirable tomaintain alow-chromi'um content in theoutput'product fromthe selective reduction or-iron tandem furnace.-These objectives" can be obtained by operating the iron-furnaceat-yarious residual iron levels within the range'f'rom' 3 to 8 percent,in that, both the carbon'and chromium contents of the iron can be expected to increase as the reduction is carried below the upper-limits ofthis range. a

The metallic phase products from the tandem furnaces, or any portion oftheseproducts, are 'brought togetherin molten form in theprecise ratiodesired in the final steel product soughtto be produced. ;-'Ihisblending or carbon dilution operation will generally result in theproduction of a composite master alloy-of carboncontent within the rangeof from 0.3 to 1 .5 percentyand a silicon content within the range'offrom 0. 1 to 0.5 percent. Thus, since the high-carbon chromium-ironalloy is diluted to an ironbase alloy, in lieu of the conventionalchromium-base alloys presently used in steel making, it is entirelypossible to reduce the carbon content in the composite master alloy tomediumand low-carbon values. Preferably, the'blending or'dilutionoperation is conducted within an intermediate holdingfurnace or directlywithin-the steel refining unit of the system. 1 1 i The master alloyrecovered from the holding furnac or formed 'in'situ in a refiningfurnace of the electric, open-hearth or converter types, is blended withany alloy ing additions, i.e., nickelfferronickel, manganese, etc.,required in accordance withthe particular type of steel being produced.The refining or finishing unit is operated in conventional fashion toeffect decarburization of the metal and adjustments are made for siliconcontent, Where desired, and the like. Undesirable constituents can beremoved during the refining melt or other constituents maybe added toobtain the desired grade specifications for the steel produced. Chromiumadjustments can be made directly during the finishing heat by oxidizingany excess chromium into the slag. On the other hand, assuming a correctchromium balance has been obtained in the initial smelting and blendingoperations conducted towards the production of the master alloy, it isdesirable, following completion of the oxygen decarburization in thefinishing furnace, to treatthe melt with a small quantity of 'anoncarbonaceous reducing agent to return to the steel any, chromiumoxidized into the slag phase during the oxidation reactions. Thefinishedsteel is then recovered from the steel furnace and is treated byconventional working methods for conversion to consumer products.

As will be readily-appreciated,; in lieu of the alloying additions tothe refining furnace, any alloying metals other than the iron andchromium contents of the master alloy required in' the finished steelcould be carried into the master alloy in whole or in part by directreduction from .an oxidic additive to. the original oreor blended-orefrac; tion charged to the iron-chrome smelting furnace. For example, ifa nickel-chromium stainless steel is' desired, a nickel-iron or nickelore could be blended with the chrome-iron fraction chargedto theallow-furnace as a combined source of nickel and iron. The nickel wouldbe reduced initially to form a ferro nickel'alloy, whereas continuedreduction would provide a metal phase product or crude high-carbon alloyof combined iron, nickel and chromium contents for ultimate blendingwith the lowcarbon iron produced in the secondtandem furnace. Theresulting crude alloy would then be subjected'to the same treatmentas'described hereinbefore in connection withthe basichigh-carboniron-chromium alloyr componentof the invention. g g

' In the operation of the tandem smelting stages of the process of theinvention, .I prefer to, employ a carbonaceousreducing agent suchasbituminous or anthracite coals, lignites or lignite chars; coke' breeze,or coke, etc. The carbonaceous reductants need not beI-;.pr.0cesed t0.any

-7 particular o m and... tart. fine t und. o. be admin ably su ted tor-ue n he p oces L While' he aromas can bepra iaed; incqninn tion with y ypo smel n equ n en 'I; p f t mp y a e n: e ect ic fu nace ope ted-undecond ons, o co b ned. arc-re istance a d; .s a r ie i tane he asl ev dthon h the m ntenance Qfirelat e y sh r r s s u kto. the; sur ace the noler ag ba or by positioning the electrode tips in s-lightly submergedrelaon h p w thin. h slag ha h... incomi harsemater i uppl d t h j urceo thefslag h around the peripher l po ions, o theufn t a c am n. orderto maintain, he ar .z neas bstantia ly fr e o a mu ate charge, andhetenters the. calci d char e d c ly from the heat d s ag a hincoutaatherew h.

In utiliz ng he ch om um xid s a r the o car on iron furnace to upgradehe o i fraction harged. to the hig a bona oy furna pr e o. a e ag n molen torm r y. o he. e t na e. and t e a d. esi ter rac 'Qn nd'rer u tanecessary for the production of the iron-chromium metal.

- It will be read ly ppare to a y ki le metallurgist that; forparticular types of chromite charge materials, it may. p e ben ficia tom ntain t hr mi n n ores separate through the tandem reduction phases ofthe process, bringing the endproducts of the two smelting furnacestogether for the first time, in the blending of the l w-c rbon m ster.al oyhuseepa e e k ln n e utilized to feed one furnace with a sinteredchromite ore and the other with a sintered iron ore, the first furnaceoperating on' total direct reduction. for the production of a highcarbon chrome-iron alloy, with the second furnace also operating ondirect reduction for the production of low-carbon iron or semi-steel.These products would then be blended to dilute the carbon content of thealloy with the production of the desired low-carbon master alloy. Underthese conditions of operation, it becomes possible to eliminate thenecessity for recycling the slag from the iron furnace to the alloyfurnace. The exact sequence of steps involved in this type of operationhas been indicated by the dotted line showing contained on theflowsheet. 7

It is believed that the proeess of the invention will be best understoodby reference to the following specific examples str i t pp cat on o heforegoing P ciples and procedures to the. production of stainless steelsfrom a typical low-grade oxidic starting material.

EXAMPLE I Charge analyses Chromite Concentrate, percent Iron Ore,

A chromite concentrate of the foregoing analysis, in amount 4540 pounds,was blended thoroughly with 4280 pounds of iron ore of the foregoinganalysis and charged to a rotary kiln together with 1100 pounds of coalof about 70 percent fixed carbon content. The charge was preheated andprereduced in the kiln to provide a free-flowing sinter at 2250. F.which analyzed 11.2 percent chromium and 33.3 percent iron, with acarbon content of about 5.0%.

This sinter, in total amount 79l0 pounds, was. divided into two separatecharges ot 27-10 pounds and 5200 pounds, respectively.

Metal (17851135.): j Percent Cr 31.1

C 6.0 Si 1.0 Fe Bal.

Slag (2848 lbs.):

Cr. 1.0 ,Fe 1.2

The second fraction of the kiln discharge, Weighing 5200 pounds wassmelted in a second are electric furnace in the presence. of 250 poundsof'coal of 70 percent fixed carbon content to produce 2460 pounds ofiron of 1,0 percent carbon content and a recyclable chromium oxide slagcontaining about 1.0 percent residual iron.

The 1785 pounds of high-carbon chrome-iron from the first tandem furnaceand the 2460 pounds of low: carbon iron from the second tandem furnacewere recombined in a steel refining furnace with a lime flux and blownwith oxygen to produce 4080pounds of a stand- 'ard grade steelcontaining 19.7 percent chromium and 0.03. percent carbon.

EXAMPLE n Metal (1665 lbs): Percent Cr 52.0 C 6.0 Si 1.0 Fe Bal.

Slag (2140 lbs.)

Cr 1.7 Fe 1.0

A second kiln was charged with 4400 pounds of iron ore of the foregoinganalysis, 600 pounds. of lime, and 900 pounds of coal (70% F .C.). Thehot kiln discharge, in amount 4230 pounds, analyzing 57 percent iron and5 percent carbon, was charged to a second electric furnacetogether with290 pounds of coal (70% RC.) and smelted therein with the production of2520 pounds of semi-steel of 0.5 percent carbon.

The 1665 pounds of chrome-iron from the first furmace and the 2520pounds of semi-steel from the second furnace were combined in a steelrefining furnace and blown with oxygen to provide 4050 pounds of steelof the following analysis:

"ffI-Iaving'thus described the subject inatter of'm-yin- Yentionjwhatit"'is"desired to secure byL'ettersPatent is: 1 Process forthe'production'of alloyed steel from ores of; chromium oxide and ironoxide that; comprises, subj'ecting a firstore fraction ofmixedchromiumand iron oxide contents tc-reduction smelting in the presence of acarbonaceous reducing agent in an amount suificient to efifect reductionto the metallic state'of substantially alloftheiron oxide and chromiumoxide contained therein with the production of a crude high-carboniron-chromium alloy and a waste slag product, subjecting a second orefraction containing a predominant proportion of iron oxide to reductionsmelting in the presence of a carbonaceous reducing agent in an amountcontrolled to effect the selective reduction to the metallic state ofthe major portion of the iron oxide content thereof with the productionof low-carbon metallic iron, blending said highcarbon iron-chromiumalloy with said low-carbon metallic iron to provide a master alloy ofcontrolled intermediate carbon content, and refining said master alloyas necessary for the production and recovery of a chromiumalloyed steelproduct.

2. The process as claimed in claim 1, wherein said first ore fraction isa chromite ore and said second ore fraction is an iron ore.

3. The process as claimed in claim 1, wherein said first and second orefractions are each formed by blending a chromite ore with an iron oxideore, there being recovered a chromium oxide-containing residual slagfrom said reduction smelting of the second ore fraction, and said slagis recycled to the reduction smelting operation conducted on said firstore fraction.

4. Process for the production of alloyed steel from a complex materialcomprising iron oxide and chromium oxide that comprises fluxing saidmaterial to form a composite reduction charge, subjecting a firstfraction of said composite charge to reduction smelting in the presenceof a carbonaceous reducing agent in an amount sufficient to effectreduction to the metallic state of substantially all of the iron oxideand chromium oxide contained therein with the productionof a crudehigh-carbon ironchromium alloy and a waste slag product, subjecting asecond fraction of said composite charge to reduction smelting in thepresence of a carbonaceous reducing agent in an amount controlled toeffect the selective reduction to the metallic state of the majorportion of the iron oxide content thereof with the production oflow-carbon metallic iron and a chromium oxide-containing molten slagproduct, recycling said chromium oxide-containing molten slag to thereduction smelting stage operating on the first fraction of said charge,blending said high-carbon iron-chromium alloy with said low-carbonmetallic iron to provide a master iron-chromium alloy of controlledintermediate carbon content, and refining said master alloy as necessaryfor the production and recovery of a chromium-alloyed steel product.

5. Process for the production of alloyed steel from a complex materialcomprising iron oxide and chromium oxide that comprises fluxing saidmaterial to form a composite reduction charge, subjecting a firstfraction of said composite charge to reduction smelting in the presenceof a carbonaceous reducing agent in an amount suflicient to effectreduction to the metallic state of substantially all of the iron oxideand chromium oxide contained therein with the production of a crudehigh-carbon ironchromium alloy and a waste slag product, subjecting asecond fraction of said composite charge to reduction smelting in thepresence of a carbonaceous reducing agent in an amount controlled toeffect the selective reduction to the metallic state of the majorportion of the iron oxide content thereof with the production oflow-carbon metallic iron and a chromium oxide-containing molten slagproduct, recycling said chromium oxide-containing molten slag to thereduction smelting stage operating on the first fraction of said charge,blending said high'carbon v. a r 10 s iron-chromium alloy withsaid'low-carbon metallic iron to provide a master. iron-chromium alloyof controlled intermediate carbonjcontent, refining said master alloywithin a refining furnace in the presence of a'fnon-carbonaceousrefining agent for the production and recovery of a chromium-alloyedsteel product.

6. The process as claimed in claim 5, wherein said master alloy issubjected'to refining within the refining furnace together withalnickel, alloying additive for. the production and recovery. of anickel-chromiumfalloy ed steelproduct.

7. Process for the recovery of iron and chromium in alloyed form from acomplex material comprising iron oxide and chromium oxide that comprisesfluxing said material to form a composite reduction charge, subjecting afirst portion of said composite charge to reduction smelting in thepresence of a carbonaceous reducing agent in an amount sufiicient toeffect reduction to the metallic state of substantially all of the ironoxide and chromium oxide contained therein with the production of acrude high-carbon iron-chromium alloy of predetermined ironchromiumratio and a waste slag product, subjecting a second portion of saidcomposite charge to reduction smelting in the presence of a carbonaceousreducing agent in an amount controlled to effect the selective reductionto the metallic state of the major portion of the iron oxide contentthereof with the production of lowcarbon metallic iron and a chromiumoxide-containing molten slag product, recycling said chromiumoxide-containing molten slag product to the reduction smelting stageoperating on said first charge portion, and blending said high-carboniron-chromium alloy and said low carbon metallic iron to provide aniron-chromium alloy of predetermined iron-chromium ratio andintermediate carbon content.

8. Process for the recovery of iron and chromium in alloyed form from acomplex material comprising iron oxide and chromium oxide that comprisesfluxing said material to form a composite reduction charge, subjecting afirst'portion of said composite charge to reduction smelting in thepresence of a carbonaceous reducing agent in an amount sufiicient toeffect reduction to the metallic state of substantially all of the ironoxide and chromium oxide contained therein with the production of acrude high-carbon iron-chromium alloy of predetermined ironchromiumratio and a waste slag product, subjecting a second portion of saidcomposite charge to reduction smelting in the presence of a carbonaceousreducing agent in an amount controlled to effect the selective reductionto the metallic state of that portion of the iron in excess of 38% ofthe total iron content of said second charge portion with the productionof low-carbon metallic iron and a chromium oxide-containing molten slagproduct, recycling said chromium oxide-containing molten slag product tothe reduction smelting stage operating on said first charge portion, andblending said high-carbon ironchromium alloy and said low carbonmetallic iron to provide an iron-chromium alloy of predeterminedironchromium ratio and intermediate carbon content.

9. Process for the production of alloyed steel from chrome-iron oresthat comprises, subjecting a first ore fraction to reduction smelting inthe presence of a carbonaceous reducing agent in an amount sufiicient toelfect reduction to the metallic state of substantially all of the ironoxide and chromium oxide contained therein with the production of acrude high-carbon iron-chromium alloy and a waste slag product,subjecting a second ore fraction to reduction smelting in the presenceof a carbonaceous reducing agent in an amount suflicient to effect theselective reduction to the metallic state of the major portion of theiron oxide content thereof with the production of a low-carbon metalliciron and a residual slag containing the chromium oxide content and theremainder of the iron content thereof, recycling said slag to areduction smelting operation conducted on said first ore 1 lfractiqn,blending said high-carbon i1,qzan-chnmaiwam alloy with Said low-carbonmetallie iron to provide a master alley; Of conti'olled intermediatecarbon content, and rej-I fining said master alloy as. necessaryforfthe'producltien' arid feeovery of, a chromium-alloyed steel product.

Becket et a Feb. 17 I931 Gustafsson 14, 1933 170' J ourna1 of 12 UdyNov. 2, 1937 Udy Feb. 212. 193$, Fei1;1 19.4!

e f 1 1,. 1 1 1111; 2.91. 958; A em-mum ER R E RE CES Metal s, Febr uary1949-, page; '9-I- 9 5 re1iedj

1. PROCESS FOR THE PRODUCTION OF ALLOYED STEEL FROM ORES OF CHROMIUMOXIDE AND IRON OXIDE THAT COMPRISES, SUBJECTING A FIRST ORE FRACTION OFMIXED CHROMIUM AND IRON OXIDE CONTENTS TO REDUCTION SMELTING IN THEPRESENCE OF A CARBONACEOUS REDUCING AGENT IN AN AMOUNT SUFFICIENT TOEFFECT REDUCTION TO THE METALLIC STATE OF SUBSTANTIALLY ALL OF THE IRONOXIDE AND CHROMIUM OXIDE CONTAINED THEREIN WITH THE PRODUCTION OF ACRUDE HIGH-CARBON IRON-CHROMIUM ALLOY AND A WASTER SLAG PRODUCT,SUBJECTING A SECOND ORE FRACTION CONTAINING A PREDOMINANT PROPORTION OFIRON OXIDE TO REDUCTION SMELTING IN THE PRESENCE OF A CARBONACEOUSREDUCING AGENT IN AN AMOUNT CONTROLLED TO EFFECT THE SELECTIVE REDUCTIONTO THE METALLIC STATE OF THE MAJOR PORTION OF THE IRON OXIDE CONTENTTHEREOF WITH THE PRODUCTION OF LOW-CARBON METALLIC IRON, BLENDING SAIDHIGHCARBON IRON-CHROMIUM ALLOY WITH SAID LOW-CARBON METALLIC IRON TOPROVIDE A MASTER ALLOY OF CONTROLLED INTERMEDIATE CARBON CONTENT, ANDREFINING SAID MASTER ALLOY AS NECESSARY FOR THE PRODUCTION AND RECOVERYOF A CHROMIUMALLOYED STEEL PRODUCT.